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libjava/classpath/vm/reference/java/lang/reflect/Method.java
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libjava/classpath/vm/reference/java/lang/reflect/Method.java
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/* java.lang.reflect.Method - reflection of Java methods
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Copyright (C) 1998, 2001, 2002 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang.reflect;
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import java.util.Arrays;
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/**
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* The Method class represents a member method of a class. It also allows
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* dynamic invocation, via reflection. This works for both static and
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* instance methods. Invocation on Method objects knows how to do
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* widening conversions, but throws {@link IllegalArgumentException} if
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* a narrowing conversion would be necessary. You can query for information
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* on this Method regardless of location, but invocation access may be limited
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* by Java language access controls. If you can't do it in the compiler, you
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* can't normally do it here either.<p>
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*
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* <B>Note:</B> This class returns and accepts types as Classes, even
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* primitive types; there are Class types defined that represent each
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* different primitive type. They are <code>java.lang.Boolean.TYPE,
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* java.lang.Byte.TYPE,</code>, also available as <code>boolean.class,
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* byte.class</code>, etc. These are not to be confused with the
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* classes <code>java.lang.Boolean, java.lang.Byte</code>, etc., which are
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* real classes.<p>
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*
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* Also note that this is not a serializable class. It is entirely feasible
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* to make it serializable using the Externalizable interface, but this is
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* on Sun, not me.
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*
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* @author John Keiser
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* @author Eric Blake <ebb9@email.byu.edu>
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* @see Member
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* @see Class
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* @see java.lang.Class#getMethod(String,Object[])
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* @see java.lang.Class#getDeclaredMethod(String,Object[])
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* @see java.lang.Class#getMethods()
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* @see java.lang.Class#getDeclaredMethods()
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* @since 1.1
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* @status updated to 1.4
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*/
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public final class Method
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extends AccessibleObject implements Member
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{
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Class declaringClass;
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String name;
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int slot;
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/**
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* This class is uninstantiable.
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*/
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private Method(Class declaringClass, String name, int slot)
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{
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this.declaringClass = declaringClass;
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this.name = name;
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this.slot = slot;
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}
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/**
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* Gets the class that declared this method, or the class where this method
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* is a non-inherited member.
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* @return the class that declared this member
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*/
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public Class getDeclaringClass()
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{
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return declaringClass;
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}
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/**
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* Gets the name of this method.
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* @return the name of this method
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*/
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public String getName()
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{
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return name;
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}
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/**
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* Gets the modifiers this method uses. Use the <code>Modifier</code>
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* class to interpret the values. A method can only have a subset of the
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* following modifiers: public, private, protected, abstract, static,
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* final, synchronized, native, and strictfp.
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*
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* @return an integer representing the modifiers to this Member
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* @see Modifier
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*/
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public native int getModifiers();
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/**
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* Gets the return type of this method.
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* @return the type of this method
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*/
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public native Class getReturnType();
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/**
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* Get the parameter list for this method, in declaration order. If the
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* method takes no parameters, returns a 0-length array (not null).
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*
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* @return a list of the types of the method's parameters
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*/
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public native Class[] getParameterTypes();
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/**
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* Get the exception types this method says it throws, in no particular
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* order. If the method has no throws clause, returns a 0-length array
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* (not null).
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*
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* @return a list of the types in the method's throws clause
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*/
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public native Class[] getExceptionTypes();
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/**
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* Compare two objects to see if they are semantically equivalent.
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* Two Methods are semantically equivalent if they have the same declaring
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* class, name, parameter list, and return type.
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*
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* @param o the object to compare to
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* @return <code>true</code> if they are equal; <code>false</code> if not
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*/
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public boolean equals(Object o)
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{
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// Implementation note:
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// The following is a correct but possibly slow implementation.
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//
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// This class has a private field 'slot' that could be used by
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// the VM implementation to "link" a particular method to a Class.
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// In that case equals could be simply implemented as:
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//
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// if (o instanceof Method)
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// {
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// Method m = (Method)o;
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// return m.declaringClass == this.declaringClass
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// && m.slot == this.slot;
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// }
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// return false;
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//
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// If a VM uses the Method class as their native/internal representation
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// then just using the following would be optimal:
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//
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// return this == o;
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//
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if (!(o instanceof Method))
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return false;
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Method that = (Method)o;
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if (this.getDeclaringClass() != that.getDeclaringClass())
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return false;
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if (!this.getName().equals(that.getName()))
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return false;
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if (this.getReturnType() != that.getReturnType())
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return false;
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if (!Arrays.equals(this.getParameterTypes(), that.getParameterTypes()))
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return false;
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return true;
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}
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/**
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* Get the hash code for the Method. The Method hash code is the hash code
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* of its name XOR'd with the hash code of its class name.
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*
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* @return the hash code for the object
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*/
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public int hashCode()
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{
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return getDeclaringClass().getName().hashCode() ^ getName().hashCode();
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}
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/**
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* Get a String representation of the Method. A Method's String
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* representation is "<modifiers> <returntype>
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* <methodname>(<paramtypes>) throws <exceptions>", where
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* everything after ')' is omitted if there are no exceptions.<br> Example:
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* <code>public static int run(java.lang.Runnable,int)</code>
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*
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* @return the String representation of the Method
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*/
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public String toString()
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{
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// 128 is a reasonable buffer initial size for constructor
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StringBuffer sb = new StringBuffer(128);
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Modifier.toString(getModifiers(), sb).append(' ');
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sb.append(getUserTypeName(getReturnType().getName())).append(' ');
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sb.append(getDeclaringClass().getName()).append('.');
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sb.append(getName()).append('(');
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Class[] c = getParameterTypes();
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if (c.length > 0)
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{
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sb.append(getUserTypeName(c[0].getName()));
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for (int i = 1; i < c.length; i++)
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sb.append(',').append(getUserTypeName(c[i].getName()));
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}
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sb.append(')');
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c = getExceptionTypes();
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if (c.length > 0)
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{
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sb.append(" throws ").append(c[0].getName());
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for (int i = 1; i < c.length; i++)
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sb.append(',').append(c[i].getName());
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}
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return sb.toString();
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}
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private static String getUserTypeName(String typeSpec)
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{
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int pos = 0;
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String typeName = "";
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String arrayPart = "";
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while (typeSpec.charAt(pos) == '[')
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{
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arrayPart += "[]";
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++pos;
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}
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switch (typeSpec.charAt(pos))
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{
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case 'Z':
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typeName = "boolean";
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break;
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case 'B':
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typeName = "byte";
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break;
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case 'C':
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typeName = "char";
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break;
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case 'D':
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typeName = "double";
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break;
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case 'F':
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typeName = "float";
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break;
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case 'I':
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typeName = "int";
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break;
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case 'J':
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typeName = "long";
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break;
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case 'S':
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typeName = "short";
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break;
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case 'L':
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typeName = typeSpec.substring(pos + 1, typeSpec.length() - 1);
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break;
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default:
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typeName = typeSpec;
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break;
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}
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return typeName + arrayPart;
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}
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/**
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* Invoke the method. Arguments are automatically unwrapped and widened,
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* and the result is automatically wrapped, if needed.<p>
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*
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* If the method is static, <code>o</code> will be ignored. Otherwise,
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* the method uses dynamic lookup as described in JLS 15.12.4.4. You cannot
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* mimic the behavior of nonvirtual lookup (as in super.foo()). This means
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* you will get a <code>NullPointerException</code> if <code>o</code> is
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* null, and an <code>IllegalArgumentException</code> if it is incompatible
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* with the declaring class of the method. If the method takes 0 arguments,
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* you may use null or a 0-length array for <code>args</code>.<p>
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*
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* Next, if this Method enforces access control, your runtime context is
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* evaluated, and you may have an <code>IllegalAccessException</code> if
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* you could not acces this method in similar compiled code. If the method
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* is static, and its class is uninitialized, you trigger class
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* initialization, which may end in a
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* <code>ExceptionInInitializerError</code>.<p>
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*
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* Finally, the method is invoked. If it completes normally, the return value
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* will be null for a void method, a wrapped object for a primitive return
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* method, or the actual return of an Object method. If it completes
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* abruptly, the exception is wrapped in an
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* <code>InvocationTargetException</code>.
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*
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* @param o the object to invoke the method on
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* @param args the arguments to the method
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* @return the return value of the method, wrapped in the appropriate
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* wrapper if it is primitive
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* @throws IllegalAccessException if the method could not normally be called
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* by the Java code (i.e. it is not public)
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* @throws IllegalArgumentException if the number of arguments is incorrect;
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* if the arguments types are wrong even with a widening conversion;
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* or if <code>o</code> is not an instance of the class or interface
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* declaring this method
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* @throws InvocationTargetException if the method throws an exception
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* @throws NullPointerException if <code>o</code> is null and this field
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* requires an instance
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* @throws ExceptionInInitializerError if accessing a static method triggered
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* class initialization, which then failed
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*/
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public Object invoke(Object o, Object[] args)
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throws IllegalAccessException, InvocationTargetException
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{
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return invokeNative(o, args, declaringClass, slot);
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}
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/*
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* NATIVE HELPERS
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*/
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private native Object invokeNative(Object o, Object[] args,
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Class declaringClass, int slot)
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throws IllegalAccessException, InvocationTargetException;
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}
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